Transmission circuit



Sept. 19, 1939. 7 2,173,559

r l. A. MITCHELL TRANSMISSION CIRCUIT Orig inal Filed Oct. 26, 1957 Tp Ta P." Efi S. P331? sa SOURCE LOAD x 7 P2 v52 P4 54 T; m

INVENTOI? ZM Q' W Patented Sept. 19, 1939 UNITED STATES PATENT OFFICE Application October 26, 1937, Serial No. 171,095 Renewed July 18, 1939 4 Claims My invention relates to transmission circuits in which alternating currents are transmitted between separated or distant points. In such instances it is often desirable to arrange the circuit in such manner as to provide a substitute circuit in the event that the primary line develops a defect. Many such circuits have been heretofore developed, but in the majority of them certain defects in the line, such as short circuits, necessitate the development of complicated switching mechanisms to remove the principal line in order to eliminate the short circuit effects.

It is an object of my invention to permit the automatic operation of either the primary or substitute line.

It is a further object of my invention to permit such alternate operation without any switching mechanism whatsoever.

The invention can be better understood from the following description when considered together with the attached drawing in which The single figure of the drawing is a schematic circuit disclosing the said invention.

In the figure, TI and T2 are transformers, the

35 primaries of which are connected in series, and to the source of alternating current which may be a generator, a transformer, a speech amplifier or any piece of similar electrical equipment. PI and P2 represent the two transformer primaries and Si and S2 the secondaries. Transformers T3 and T4 are connected to the circuit load at their secondaries which are represented in series by S3 and S4. Windings P3 and P4 are the two primary windings of transformers T3 and T4.

5 Winding SI is connected to winding P3 and winding S2 to P4. The midpoints of SI and S2 are connected together and likewise the midpoints of P3 and P4 are joined.

The power in the circuit is normally trans- 40 mitted through both sets of wires. In the event that a failure occurs in one of the lines due to a short circuit, the transformer included within such line is in effect shorted. The circuit is then operating through one line and one set of trans- 45 formers only. By proper design the transformers can be constructed to operate efiiciently at twice normal voltage. Since the impedances presented by the line to the source and load remain the same, no high currents can flow in the shorted 50 transformers.

In the event that one wire opens, the transformers to which said wire is connected operate at one-half voltage, and the others at slightly above normal voltage. The connections between 55 the midpoints of SI and S2 and P3 and P4 permit the use of the complete wire in the defective line, and both wires of the remaining line to be used as a complete circuit. The power distribution through the lines is altered but, otherwise, the transmission characteristics of the unit remain constant.

My invention has been described herein in particular embodiments for purposes of illustration.

It will be understood, however, that the inven tion may be susceptible of various changes and modifications without departing from the scope and spirit of the invention as set forth in the appended claims.

I claim:

1. In a transmission line, two transformers each having an input winding and tapped secondary winding, two additional transformers each having an output winding and tapped primary winding, the taps in the secondaries con nected together, the taps in the primaries connected together, the input windings connected in series, the output windings connected in series, each tapped secondary connected to one tapped primary.

2. In a transmission line, two transformers each having an input winding and centrally tapped secondary winding, two additional transformers each having an output winding and centrally tapped primary winding, the taps in the secondaries connected together, the taps in the primaries connected together, the input windings connected in series, the output windings connected in series, each tapped secondary connected to one tapped primary.

3. In a transmission line, two similar transformers each having an input winding and tapped secondary winding, two additional, similar transformers each having an output winding and tapped primary winding, the taps in the secondaries connected together, the taps in the primaries connected together, the input windings connected in series, the output windings connected in series, each tapped secondary connected to one tapped primary.

4. In a transmission line, two similar transformers each having an input winding and centrally tapped secondary winding, two additional similar transformers each having an output winding and centrally tapped primary winding, the taps in the secondaries connected together, the taps in the primaries connected together, the input windings connected in series, the output windings connected in series, each tapped secondary connected to one tapped primary.

ISAAC A. MITCHELL. 

